The present invention relates to a fuel injection pump of the distributor type for distributing and supplying fuel to the combustion chambers in an internal combustion engine, and more particularly, it relates to a fuel injection pump of the distributor type most suitable for use in diesel engines.
The distributive fuel injection pump of this type is disclosed in the Japanese Patent Publication No. Sho-51/34936. The fuel injection pump disclosed in this publication is provided with a fuel adjusting mechanism for adjusting the amount of fuel fed out of the pump. The fuel adjusting mechanism includes a fuel escaping passage which communicates with the pumping chamber in the fuel injection pump, and an electromagnetic valve for opening and closing the fuel escaping passage. The operation of this electromagnetic valve is controlled to open the fuel escaping passage after a predetermined delay time has elapsed since the fuel was pressurized in the pumping chamber. More specifically, the pressurized fuel which is to be fed from the pumping chamber into the combustion chamber of the engine is not fed from the pumping chamber into the combustion chamber, but escapes through the fuel escaping passage when the electromagnetic valve opens the fuel escaping passage, thereby enabling the amount of fuel fed by the fuel injection pump to be adjusted. In other words, the amount of fuel injected by the fuel injection pump can be controlled by the delay time starting from when the fuel is pressurized and ending when the electromagnetic valve is opened.
The mechanism for controlling the operation of the electromagnetic valve detects the rotary angle of the driving shaft of the fuel injection pump, the rotary angle corresponding to the time at which the fuel in the pumping chamber starts to be pressurized. It causes the electromagnetic valve to be opened after the predetermined delay time has elapsed since the start of the fuel pressurization.
In the fuel injection pump disclosed in the Japanese Patent Publication, however, the sensor for detecting the rotary angle of the driving shaft is fixedly located. When the fuel injection time adjusting means or timer arranged in the fuel injection pump, operates in accordance with the operation of the engine, therefore, the phase angle between the sensor around the axis of the driving shaft and the driving shaft itself is incorrect. In short, the phase angle is shifted from its correct one. As a result, the fuel pressure starting time obtained by detecting the rotary angle of the driving shaft by means of the sensor does not coincide with the actual fuel pressure starting time. This means that the delay time starting from the pressurizing of the fuel and ending in the opening of the electromagnetic valve is shifted from its desired value, thereby making it impossible to accurately control the amount of fuel injected by the fuel injection pump.